From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CEE7DC43332 for ; Thu, 19 Mar 2020 16:23:36 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8B80C2072C for ; Thu, 19 Mar 2020 16:23:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MAmIRUDK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8B80C2072C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40358 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jExxH-0002LS-No for qemu-devel@archiver.kernel.org; Thu, 19 Mar 2020 12:23:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48005) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jExwY-0001q7-QQ for qemu-devel@nongnu.org; Thu, 19 Mar 2020 12:22:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jExwW-00005M-Rh for qemu-devel@nongnu.org; Thu, 19 Mar 2020 12:22:50 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:49190) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jExwW-00005E-MS for qemu-devel@nongnu.org; Thu, 19 Mar 2020 12:22:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584634968; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5E3CHZq6olelajyC8ii74mtawhV43FEdby2RdOlWkSM=; b=MAmIRUDKSgcC4hDXk452Y+h125gpP9J09UCNAk1WTPQJGExk39fDGYy2jWSw5fbe72dC6A vC90+kKC0W6xFTBuOLt9AjEtCdCmT4Hmy90gNTYfWlO0+RSx2M1bPFZYo/mbYpexquRdev Isn2vgBScExOyIjqsvaoiY9om+5S8nw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-268-LCu4D0u2OPaY_HwWQIGmzA-1; Thu, 19 Mar 2020 12:22:43 -0400 X-MC-Unique: LCu4D0u2OPaY_HwWQIGmzA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 575C7801E53; Thu, 19 Mar 2020 16:22:40 +0000 (UTC) Received: from w520.home (ovpn-112-162.phx2.redhat.com [10.3.112.162]) by smtp.corp.redhat.com (Postfix) with ESMTP id A893760BFB; Thu, 19 Mar 2020 16:22:38 +0000 (UTC) Date: Thu, 19 Mar 2020 10:22:38 -0600 From: Alex Williamson To: Kirti Wankhede Subject: Re: [PATCH v14 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking. Message-ID: <20200319102238.77686a08@w520.home> In-Reply-To: References: <1584560474-19946-1-git-send-email-kwankhede@nvidia.com> <1584560474-19946-5-git-send-email-kwankhede@nvidia.com> <20200318214500.1a0cb985@w520.home> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com, yi.l.liu@intel.com, cjia@nvidia.com, kvm@vger.kernel.org, eskultet@redhat.com, ziye.yang@intel.com, qemu-devel@nongnu.org, cohuck@redhat.com, shuangtai.tst@alibaba-inc.com, dgilbert@redhat.com, zhi.a.wang@intel.com, mlevitsk@redhat.com, pasic@linux.ibm.com, aik@ozlabs.ru, eauger@redhat.com, felipe@nutanix.com, jonathan.davies@nutanix.com, yan.y.zhao@intel.com, changpeng.liu@intel.com, Ken.Xue@amd.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 19 Mar 2020 20:22:41 +0530 Kirti Wankhede wrote: > On 3/19/2020 9:15 AM, Alex Williamson wrote: > > On Thu, 19 Mar 2020 01:11:11 +0530 > > Kirti Wankhede wrote: > > > >> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations: > >> - Start dirty pages tracking while migration is active > >> - Stop dirty pages tracking. > >> - Get dirty pages bitmap. Its user space application's responsibility to > >> copy content of dirty pages from source to destination during migration. > >> > >> To prevent DoS attack, memory for bitmap is allocated per vfio_dma > >> structure. Bitmap size is calculated considering smallest supported page > >> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled > >> > >> Bitmap is populated for already pinned pages when bitmap is allocated for > >> a vfio_dma with the smallest supported page size. Update bitmap from > >> pinning functions when tracking is enabled. When user application queries > >> bitmap, check if requested page size is same as page size used to > >> populated bitmap. If it is equal, copy bitmap, but if not equal, return > >> error. > >> > >> Signed-off-by: Kirti Wankhede > >> Reviewed-by: Neo Jia > >> --- > >> drivers/vfio/vfio_iommu_type1.c | 205 +++++++++++++++++++++++++++++++++++++++- > >> 1 file changed, 203 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >> index 70aeab921d0f..d6417fb02174 100644 > >> --- a/drivers/vfio/vfio_iommu_type1.c > >> +++ b/drivers/vfio/vfio_iommu_type1.c > >> @@ -71,6 +71,7 @@ struct vfio_iommu { > >> unsigned int dma_avail; > >> bool v2; > >> bool nesting; > >> + bool dirty_page_tracking; > >> }; > >> > >> struct vfio_domain { > >> @@ -91,6 +92,7 @@ struct vfio_dma { > >> bool lock_cap; /* capable(CAP_IPC_LOCK) */ > >> struct task_struct *task; > >> struct rb_root pfn_list; /* Ex-user pinned pfn list */ > >> + unsigned long *bitmap; > > > > We've made the bitmap a width invariant u64 else, should be here as > > well. > > > >> }; > >> > >> struct vfio_group { > >> @@ -125,7 +127,10 @@ struct vfio_regions { > >> #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \ > >> (!list_empty(&iommu->domain_list)) > >> > >> +#define DIRTY_BITMAP_BYTES(n) (ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE) > >> + > >> static int put_pfn(unsigned long pfn, int prot); > >> +static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu); > >> > >> /* > >> * This code handles mapping and unmapping of user data buffers > >> @@ -175,6 +180,55 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old) > >> rb_erase(&old->node, &iommu->dma_list); > >> } > >> > >> +static int vfio_dma_bitmap_alloc(struct vfio_iommu *iommu, uint64_t pgsize) > >> +{ > >> + struct rb_node *n = rb_first(&iommu->dma_list); > >> + > >> + for (; n; n = rb_next(n)) { > >> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node); > >> + struct rb_node *p; > >> + unsigned long npages = dma->size / pgsize; > >> + > >> + dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL); > >> + if (!dma->bitmap) { > >> + struct rb_node *p = rb_prev(n); > >> + > >> + for (; p; p = rb_prev(p)) { > >> + struct vfio_dma *dma = rb_entry(n, > >> + struct vfio_dma, node); > >> + > >> + kfree(dma->bitmap); > >> + dma->bitmap = NULL; > >> + } > >> + return -ENOMEM; > >> + } > >> + > >> + if (RB_EMPTY_ROOT(&dma->pfn_list)) > >> + continue; > >> + > >> + for (p = rb_first(&dma->pfn_list); p; p = rb_next(p)) { > >> + struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn, > >> + node); > >> + > >> + bitmap_set(dma->bitmap, > >> + (vpfn->iova - dma->iova) / pgsize, 1); > >> + } > >> + } > >> + return 0; > >> +} > >> + > >> +static void vfio_dma_bitmap_free(struct vfio_iommu *iommu) > >> +{ > >> + struct rb_node *n = rb_first(&iommu->dma_list); > >> + > >> + for (; n; n = rb_next(n)) { > >> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node); > >> + > >> + kfree(dma->bitmap); > >> + dma->bitmap = NULL; > >> + } > >> +} > >> + > >> /* > >> * Helper Functions for host iova-pfn list > >> */ > >> @@ -567,6 +621,14 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, > >> vfio_unpin_page_external(dma, iova, do_accounting); > >> goto pin_unwind; > >> } > >> + > >> + if (iommu->dirty_page_tracking) { > >> + unsigned long pgshift = > >> + __ffs(vfio_pgsize_bitmap(iommu)); > >> + > >> + bitmap_set(dma->bitmap, > >> + (vpfn->iova - dma->iova) >> pgshift, 1); > >> + } > >> } > >> > >> ret = i; > >> @@ -801,6 +863,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma) > >> vfio_unmap_unpin(iommu, dma, true); > >> vfio_unlink_dma(iommu, dma); > >> put_task_struct(dma->task); > >> + kfree(dma->bitmap); > >> kfree(dma); > >> iommu->dma_avail++; > >> } > >> @@ -831,6 +894,50 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu) > >> return bitmap; > >> } > >> > >> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova, > >> + size_t size, uint64_t pgsize, > >> + unsigned char __user *bitmap) > > > > And here, why do callers cast to an unsigned char pointer when we're > > going to cast to a void pointer anyway? Should be a u64 __user pointer. > > > >> +{ > >> + struct vfio_dma *dma; > >> + unsigned long pgshift = __ffs(pgsize); > >> + unsigned int npages, bitmap_size; > >> + > >> + dma = vfio_find_dma(iommu, iova, 1); > >> + > >> + if (!dma) > >> + return -EINVAL; > >> + > >> + if (dma->iova != iova || dma->size != size) > >> + return -EINVAL; > >> + > >> + npages = dma->size >> pgshift; > >> + bitmap_size = DIRTY_BITMAP_BYTES(npages); > >> + > >> + /* mark all pages dirty if all pages are pinned and mapped. */ > >> + if (dma->iommu_mapped) > >> + bitmap_set(dma->bitmap, 0, npages); > >> + > >> + if (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size)) > >> + return -EFAULT; > >> + > >> + return 0; > >> +} > >> + > >> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size) > >> +{ > >> + uint64_t bsize; > >> + > >> + if (!npages || !bitmap_size || bitmap_size > UINT_MAX) > > > > As commented previously, how do we derive this UINT_MAX limitation? > > > > Sorry, I missed that earlier > > > UINT_MAX seems arbitrary, is this specified in our API? The size of a > > vfio_dma is limited to what the user is able to pin, and therefore > > their locked memory limit, but do we have an explicit limit elsewhere > > that results in this limit here. I think a 4GB bitmap would track > > something like 2^47 bytes of memory, that's pretty excessive, but still > > an arbitrary limit. > > There has to be some upper limit check. In core KVM, in > virt/kvm/kvm_main.c there is max number of pages check: > > if (new.npages > KVM_MEM_MAX_NR_PAGES) > > Where > /* > * Some of the bitops functions do not support too long bitmaps. > * This number must be determined not to exceed such limits. > */ > #define KVM_MEM_MAX_NR_PAGES ((1UL << 31) - 1) > > Though I don't know which bitops functions do not support long bitmaps. > > Something similar as above can be done or same as you also mentioned of > 4GB bitmap limit? that is U32_MAX instead of UINT_MAX? Let's see, we use bitmap_set(): void bitmap_set(unsigned long *map, unsigned int start, unsigned int nbits) So we're limited to an unsigned int number of bits, but for an unaligned, multi-bit operation this will call __bitmap_set(): void __bitmap_set(unsigned long *map, unsigned int start, int len) So we're down to a signed int number of bits (seems like an API bug in bitops there), so it makes sense that KVM is testing against MAX_INT number of pages, ie. number of bits. But that still suggests a bitmap size of MAX_UINT is off by a factor of 16. So we can have 2^31 bits divided by 2^3 bits/byte yields a maximum bitmap size of 2^28 (ie. 256MB), which maps 2^31 * 2^12 = 2^43 (8TB) on a 4K system. Let's fix the limit check and put a nice comment explaining it. Thanks, Alex > >> + return -EINVAL; > >> + > >> + bsize = DIRTY_BITMAP_BYTES(npages); > >> + > >> + if (bitmap_size < bsize) > >> + return -EINVAL; > >> + > >> + return 0; > >> +} > >> + > >> static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> struct vfio_iommu_type1_dma_unmap *unmap) > >> { > > > > We didn't address that vfio_dma_do_map() needs to kvzalloc a bitmap for > > any new vfio_dma created while iommu->dirty_page_tracking = true. > > > > Good point. Adding it. > > Thanks, > Kirti > > >> @@ -2278,6 +2385,93 @@ static long vfio_iommu_type1_ioctl(void *iommu_data, > >> > >> return copy_to_user((void __user *)arg, &unmap, minsz) ? > >> -EFAULT : 0; > >> + } else if (cmd == VFIO_IOMMU_DIRTY_PAGES) { > >> + struct vfio_iommu_type1_dirty_bitmap dirty; > >> + uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START | > >> + VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP | > >> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP; > >> + int ret = 0; > >> + > >> + if (!iommu->v2) > >> + return -EACCES; > >> + > >> + minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap, > >> + flags); > >> + > >> + if (copy_from_user(&dirty, (void __user *)arg, minsz)) > >> + return -EFAULT; > >> + > >> + if (dirty.argsz < minsz || dirty.flags & ~mask) > >> + return -EINVAL; > >> + > >> + /* only one flag should be set at a time */ > >> + if (__ffs(dirty.flags) != __fls(dirty.flags)) > >> + return -EINVAL; > >> + > >> + if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) { > >> + uint64_t pgsize = 1 << __ffs(vfio_pgsize_bitmap(iommu)); > >> + > >> + mutex_lock(&iommu->lock); > >> + if (!iommu->dirty_page_tracking) { > >> + ret = vfio_dma_bitmap_alloc(iommu, pgsize); > >> + if (!ret) > >> + iommu->dirty_page_tracking = true; > >> + } > >> + mutex_unlock(&iommu->lock); > >> + return ret; > >> + } else if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) { > >> + mutex_lock(&iommu->lock); > >> + if (iommu->dirty_page_tracking) { > >> + iommu->dirty_page_tracking = false; > >> + vfio_dma_bitmap_free(iommu); > >> + } > >> + mutex_unlock(&iommu->lock); > >> + return 0; > >> + } else if (dirty.flags & > >> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) { > >> + struct vfio_iommu_type1_dirty_bitmap_get range; > >> + unsigned long pgshift; > >> + size_t data_size = dirty.argsz - minsz; > >> + uint64_t iommu_pgsize = > >> + 1 << __ffs(vfio_pgsize_bitmap(iommu)); > >> + > >> + if (!data_size || data_size < sizeof(range)) > >> + return -EINVAL; > >> + > >> + if (copy_from_user(&range, (void __user *)(arg + minsz), > >> + sizeof(range))) > >> + return -EFAULT; > >> + > >> + /* allow only min supported pgsize */ > >> + if (range.bitmap.pgsize != iommu_pgsize) > >> + return -EINVAL; > >> + if (range.iova & (iommu_pgsize - 1)) > >> + return -EINVAL; > >> + if (!range.size || range.size & (iommu_pgsize - 1)) > >> + return -EINVAL; > >> + if (range.iova + range.size < range.iova) > >> + return -EINVAL; > >> + if (!access_ok((void __user *)range.bitmap.data, > >> + range.bitmap.size)) > >> + return -EINVAL; > >> + > >> + pgshift = __ffs(range.bitmap.pgsize); > >> + ret = verify_bitmap_size(range.size >> pgshift, > >> + range.bitmap.size); > >> + if (ret) > >> + return ret; > >> + > >> + mutex_lock(&iommu->lock); > >> + if (iommu->dirty_page_tracking) > >> + ret = vfio_iova_dirty_bitmap(iommu, range.iova, > >> + range.size, range.bitmap.pgsize, > >> + (unsigned char __user *)range.bitmap.data); > >> + else > >> + ret = -EINVAL; > >> + mutex_unlock(&iommu->lock); > >> + > >> + return ret; > >> + } > >> } > >> > >> return -ENOTTY; > >> @@ -2345,10 +2539,17 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu, > >> > >> vaddr = dma->vaddr + offset; > >> > >> - if (write) > >> + if (write) { > >> *copied = __copy_to_user((void __user *)vaddr, data, > >> count) ? 0 : count; > >> - else > >> + if (*copied && iommu->dirty_page_tracking) { > >> + unsigned long pgshift = > >> + __ffs(vfio_pgsize_bitmap(iommu)); > >> + > >> + bitmap_set(dma->bitmap, offset >> pgshift, > >> + *copied >> pgshift); > >> + } > >> + } else > > > > Great, thanks for adding this! > > > >> *copied = __copy_from_user(data, (void __user *)vaddr, > >> count) ? 0 : count; > >> if (kthread) > > >